The present invention concerns central heating and/or hot-water production installation, of the type using at least one conventional source of heat of the liquid or gaseous fuel boiler type, and at least one thermodynamic heat pump source of heat, particularly of the compression heat cycle formed by a closed circuit in which flows a refrigerating fluid and comprising in series, in a way known per se, an evaporator, a compressor, a condenser forming the thermodynamic heat source properly speaking, and an expansion means for the condensed refrigerating fluid, one or more circuits for the circulation of the heat-carrying fluid of the central heating and for the production of sanitary or industrial hot water being furthermore provided and arranged to be the seat of heat exchanges with said above-mentioned heat sources.
Of course, this kind of installation may comprise one or more boilers and one or more heat circuits according to the application contemplated. These installations may in this respect be provided for heating living, industrial use, commercial or else agricultural premises for the whole or part of the year, and the hot water produced may also be for different uses, for example for sanitary or industrial use. As for the heat-carrying fluid of the central heating, it will be readily understood that it may be any appropriate fluid, for example water or air.
Installations of the above-defined type are known, i.e. in brief installations using heat sources of different kinds, on the one hand conventional of the boiler kind consuming a liquid or gaseous fuel, on the other hand of the heat pump thermodynamic kind, the heat being taken from any cold source (outside air, river, etc.). These installations have been developed in recent years since attempts have been made to economize fuels.
However, it is observed that known installations are not yet adapted for obtaining the best possible energy yields. In particular, conventional central heating boilers do not use as well as possible the energy of the fuel. They only use the lower heating power of the fuel, instead of using the higher heating power thereof. In particular, conventional boilers, whether they are used alone or in combination with the other heat sources in question, do not take advantage of the latent heat of vaporization of the water contained in the combustion gases, for the vapor is for a large part discharged into the atmosphere with the smoke; they only use the sensible heat of the combustion gases, and even so imperfectly. In fact, the combustion gases are discharged into the chimney at a temperature still relatively high, i.e. heat is still lost. Finally, there is in general an air intake to the burners which is excessive in relation to the needs of a stoechiometric combustion.
All that results in only 80 to 85% of the upper heating power of the fuel being used in such installations.
It should also be noted that the temperature of the heat-carrying fluid of conventional boilers is often maintained higher than that necessary for the central heating, because of the necessarily higher temperature which is required for the production of sanitary or industrial hot water; that makes more perceptible the weakness--relative--of the efficiency of the boiler during periods of moderate heating.
Furthermore, if we now consider no longer the boiler(s) and their efficiency, but their association, in installations of the type in question, with other heat sources of the heat pump kind, poor cooperation of these two kinds of sources is generally found, because designed separately and associated in a way which, from the point of view of energy efficiency and complementarity, is far from being ideal, at least during a considerable proportion of the year, particularly in the cold season.
As for heat pumps, it is known particularly from theory and practice that their overall energy efficiency diminishes when the temperature difference between the cold source and the hot source increases, i.e. especially when the temperature of the cold source diminishes, which is the case as a rule in winter, precisely when the heat needs for heating the premises are the highest. Furthermore, even as far as the production of sanitary hot water is concerned, a temperature of 60.degree. to 65.degree. C. must be obtained for the condenser of the heat pump concerned, assuming that the heat for the production of this hot water is taken directly from this condenser rather than from the boiler, which for low temperatures at the evaporator only allows a mediocre efficiency for the heat pump to be obtained. The ideal temperature difference between the evaporator and the condenser ranges in fact between about 40.degree. and 45.degree. C. When atmospheric air is used as the cold source, the reduction of the enthalpy of this air in winter makes this lowering of the efficiency of the heat pump particularly clear.
An additional important problem is moreover often posed in winter, when compression cycle heat pumps are used: it is the problem of icing up of the evaporator (or evaporators) whose de-icing may require the use of a supplementary source of heat, sometimes an electric heating device and which, whatever the solution chosen, contributes further to diminishing the efficiency of the heat pump (taking a part of the heat of the condenser for de-icing, or other solutions).
Finally, it should be noted that the power of the compressors is relatively limited, because of the high electric current consumed at start-up.
The aim of the present invention is generally to remedy these shortcomings found in known installations such as defined at the beginning. This aim is in particular to use better than before the heating power of the fuel, and to take advantage of the heat for vaporizing the water vapor contained in the fumes; it is to discharge this smoke into the atmosphere at the lowest possible temperature, a little above 0.degree. C., and thus finally to use in the best way possible the enthalpy of the combustion gase (sensible heat and latent heat). This aim of the invention is at the same time, in installations of the kind in question, to arrange things so that the heat pump(s) operate under conditions enabling them to reach a better efficiency and in any case under the best possible operating conditions, whether in cold or hot seasons, for central heating or for the production of sanitary or industrial hot water alone, by using in the best way possible the free enthalpy of the cold source, i.e. principally that of atmospheric air.